Bakery products, pastries and confectionery are often extruded by forcing a substance placed under pressure through a nozzle arrangement to form a strand. The strand as such may be carried away by a conveyor belt or it may be divided into short portions. The external shape, in particular the peripheral shape of the strand is dependent upon the nozzle arrangement.
From EP-A-0 704 158 a nozzle arrangement is known, which comprises an inner stationary nozzle as well as a middle and an outer nozzle, which are disposed coaxially and of which the last two are jointly rotatable. Such a nozzle arrangement is used to produce dough strands of differing cross-sectional shape, which each comprise an inner filling surrounded by two layers of dough.
From DE-A-452 211 a bread plaiting machine is known, in which three plaiting die rings deliver between two rotating drivers and are therefore interwoven along a path in the shape of a figure eight. With such a machine it is not possible to produce dough products having a filling because the filling would have to be supplied in the delivery region of the plaiting die rings between the drivers.
From EP-A-0 168 255 and EP-A-0 177 175 A2 devices for co-extruding two substances are known, which extrude an inner substance through a nozzle and an outer substance containing granular particles through a hopper surrounding the nozzle, wherein the substances are combined to form a strand. The hopper at its mouth has sharp edges so that the granular particles in the outer substance may pass onto the surface. The mouth of the hopper may be of a toothed design so that the particles also project from the surface. The composite strand is carried away by a conveyor belt. By said means it is possible to produce from two substances a bakery product, which has a rectilinear elongate shape and has granular particles at the surface.
From EP-A-0 202 143 a triple extruder is known, by means of which an inner substance is coated with a first outer substance, and the latter is coated with a second outer substance. The inner substance is fed through a middle feed channel to an inner nozzle. An outer nozzle surrounds the inner nozzle and is supplied with the first outer substance through a lateral feed channel. A hopper surrounds the outer nozzle. The second outer substance is supplied through the hopper. The outer nozzle and the hopper each form an annular space around the inner nozzle. In longitudinal section, said annular spaces have an angular shape. With such a triple extruder it is possible to produce a likewise elongate, externally rectilinear bakery product.
U.S. Pat. No. 5,120,554 describes a stand-alone nozzle head for extruding a doughy substance. The nozzle head at its periphery has a plurality of nozzle arrangements. The nozzle arrangements are formed in each case by a double nozzle for manufacturing filled bakery products. Said double nozzles each have an inner nozzle, which is supplied through an individual feed channel, and an outer nozzle. The outer nozzles are supplied via a common cylindrical feed chamber through lateral channels. The nozzle head enables simultaneous extrusion of a plurality of filled, straight strands.
From U.S. Pat. No. 5,518,749 and WO 97/25881 a method and a device for manufacturing twisted cereal products are known. A rotor, which extends through a chamber and runs into an opening of the chamber, forms an inner nozzle, through which an inner substance is feedable. A second substance is feedable through a lateral channel into the chamber. Between the opening of the chamber and the rotor there is an annular gap, through which the second substance may exit. The annular gap corresponds to an outer nozzle. When the inner nozzle rotates, a product having a twisted outer substance layer and a filling is produced. In said case, however, the twisting of the outer substance layer is highly dependent upon the properties of the outer substance, such as its flow behaviour and viscosity. The extruded cereal products therefore do not always have a sufficiently uniform shape.
The object of the invention is to provide a nozzle arrangement, a nozzle carrier and a device for extruding doughy substances, with which it is possible with a high degree of accuracy as regards weight and shape to manufacture twisted or coiled bakery and confectionery products, in which individual coiled outer strands are formed around a rectilinear middle strand.
The object is achieved according to the invention by a nozzle arrangement comprising an inner nozzle, which is disposed coaxially with an axis of rotation and has a mouth for extruding an inner substance, and at least one outer nozzle, which is rotatable about the axis of rotation and has a mouth for extruding at least one outer substance. The outer nozzle is in said case axially offset relative to the inner nozzle or disposed at a distance from the inner nozzle. It is advantageous when the inner nozzle is also rotatable about the axis of rotation. With such a nozzle arrangement it is possible to produce a bakery product comprising a middle strand, around which outer strands are coiled.
The shape and number of the outer strands are variable within a wide range by means of the shape and number of outer nozzles. A regular shape arises when a plurality of outer nozzles, through which a plurality of outer substances are feedable, are arranged distributed at regular intervals on the periphery of the inner nozzle.
According to the present invention, in longitudinal section the annular spaces formed in the nozzle carriers are in sections circular or elliptical in shape. The substance flowing into or out of the annular space or inside the annular space is therefore prevented from flowing over more or less sharp edges, which would generate turbulence in the substance. The annular spaces moreover serve as pressure compensation spaces so that it is possible to allow the substances to flow uniformly out of the mouths of the outer nozzles, and bakery products of a precisely identical outer shape and of an identical weight are obtained.
By virtue of the developments according to the present invention the nozzle carrier may be adapted to attributes of the viscous substance, such as flow volume or viscosity, by simply exchanging interchangeable parts.
For driving the nozzle carrier, a traction mechanism gearing in particular a toothed belt drive, or a toothed gearing with intersecting axes is provided, wherein in a special configuration a plurality of nozzle carriers are drivable simultaneously.
A preferred embodiment of the invention provides that the nozzle carrier(s) is (are) disposed so as to be inclined at an angle xcex1 of around 25xc2x0 to the vertical. By virtue of the inclined nozzle carrier the emerging substance encounters a support, e.g. a conveyor belt, obliquely and is therefore, as it is moved away, deformed less than would be the case if it emerged vertically.